1. Field
Various features relate to voltage control and/or monitoring circuits, and more particularly to methods and apparatuses for automatically measuring voltage of a power supply while dynamically adjusting such voltage measurements as the supply voltage changes.
2. Background
The proliferation of portable electronic devices is dependent on reliable portable power supplies/sources. Commonly used power supplies for such portable electronic devices include, for example, non-rechargeable and rechargeable batteries, battery cells, and the like. Portable electronic devices include, but are not limited to, mobile phones, wireless phones, personal computing devices, handheld computing devices, digital book readers, digital tablets, digital music players, etc. Other types of devices that may also rely on portable power supplies include electric and/or hybrid vehicles, such as cars and/or bicycles.
The proper charging and/or power management of such battery powered devices often depends on the accurate monitoring of power levels of the portable power supply (e.g., batteries, etc.). The portable power supply voltage varies depending the charge in the power supply, temperature, and/or load conditions. Portable power supply voltage is often monitored for various functions like low voltage cut off to protect the portable power supply/source e.g., battery), proper operation of a device, etc. Some present implementations for this monitoring function typically use a large resistor array to divide down the portable power supply (e.g., battery) voltage. The purpose of such large resistor array is to divide the power supply voltage sufficiently (e.g., to within a predefined range) that allows comparison to a reference band gap voltage, thereby ascertaining an actual voltage of the power supply. However, the large resistors, used to perform continuous voltage monitoring while saving power, often result take up a large footprint which is undesirable when implementing such monitoring function with a silicon die. In an alternative approach, a low-power switched capacitor circuit can be used to monitor/measure the voltage for a power supply, but this approach needs a clock source, which is not practical and/or desirable in many cases.
Therefore, there exists a need for a voltage divider circuit that overcomes the disadvantages of prior art voltage divider structures to permit efficient measuring/monitoring of voltages for a power supply.